Ignition coil controlled ignition systems for automotive vehicles in which a transistor is serially connected with the ignition coil are well known; such systems usually include a control circuit which controls the transistor to conductive state, whereupon current will flow from a source, typically the on-board network of a vehicle, including a battery, through the coil to the transistor to ground or chassis. When a sufficient amount of electromagnetic energy has been stored in the coil, the transistor is suddenly controlled to blocked state, causing an inductive high-voltage surge in the secondary of the ignition coil which provides the energy for flash-over of the spark of a spark gap, for example a spark plug. A distributor can be interposed in the secondary between the coil and the spark plug for multi-cylinder internal combustion engines. Under certain operating conditions of the vehicle, it is possible that the voltage supply exceeds a given nominal value; current through the transistor in series with the coil then will become excessive, leading to damage, and possible destruction thereof.